Conventional circulators are based on magnetic biasing and ferromagnetic materials. Despite their maturity and broad availability, conventional magnetic circulators are largely unattractive for integration, due to their bulky dimensions and the incompatibility of the magnetic materials with IC technology. Alternative approaches for magnet-less non-reciprocity based on linear and periodically time-variant circuits require either large modulation frequencies (similar to or even higher than RF frequency), which unavoidably increases the power consumption or the use of off-chip inductors that prevent full miniaturization and integration.